PASADENA, Calif. (AP) Detailed images of a comet taken by NASA's Deep Space 1 probe reveal an unexpectedly complex object with a surface of rugged terrain, rolling plains, deep fractures and very dark material, scientists said.The spacecraft, nearing the end of its useful life, flew within 1,340 miles of comet Borrelly's bowling pin-shaped nucleus on Saturday and snapped two dozen pictures.The images of the 21/2-by-5-mile nucleus revealed it was spewing three distinct columns of dust.They also showed that the nucleus' frozen core of dust and ice is coated with a pitch-black material, thought to be a mix of organic molecules."This was sort of like a Dove Bar the size of Mount Everest," said Don Yeomans, a comet expert at the National Aeronautics and Space Administration's Jet Propulsion Laboratory, where results of the flyby were displayed at a news conference Tuesday.The three jets of dust are thought to emanate from deep, well-like structures located in bowl-shaped depressions in the nucleus."These are regions of active erosion," said Larry Soderblom, a U.S. Geological Survey scientists and leader of the imaging team.All of the space probe's science instruments collected data during the encounter."They were able to see, smell and hear the atmosphere of the cometary environment," said Marc Rayman, the mission's project manager.Deep Space 1 caught Borrelly at its most active, just a week after its closest approach to the sun. The comet was 137 million miles from Earth at the time.It was only the second close-up scientists have had of a comet's nucleus. The other came in 1986 when the European Space Agency's Giotto spacecraft flew past the comet Halley. But Mr. Yeomans said Deep Space's images have higher resolution than those acquired by Giotto.The encounter was a bonus for the $164 million Deep Space 1 mission. The probe is nearly out of fuel and NASA plans to turn it off later this year.The location of the comet's nucleus within its surrounding cloud of charged particles was unexpected, said David Young, a University of Michigan scientist and leader of the mission's space physics team.Scientists had expected the nucleus to be within the center of the cloud, formed when the solar wind interacts with the dust and gas given off by the comet. Instead, the nucleus was located to one side.